1. Field of the Invention
The present invention relates to a printing medium suitable for use in ink-jet printing, a production process thereof, and an ink-jet printing method using this medium.
2. Related Background Art
An ink-jet printing method is a method in which printing is conducted by generating and flying droplets of an ink by one of various ink ejection systems, for example, an electrostatic attraction system, a system using a piezoelectric element to give an ink a mechanical vibration or change, or a system in which an ink is heated to form bubbles in the ink to use the pressure thus produced, and applying the droplets in whole or in part to a printing material such as paper or a plastic film coated with an ink-receiving layer. The ink-jet printing method attracts attention as a printing method which scarcely produces noise and can conduct high-speed printing and multi-color printing.
As inks for ink-jet printing, inks comprising water as a principal component are mainly used from the viewpoints of safety, printability and the like. A polyhydric alcohol and/or the like are often added to such inks with a view toward preventing clogging of orifices and improving ejection stability.
As printing materials suitable for use in ink-jet printing, there have hitherto been used glossy paper as described in Japanese Patent Publication No. 3-25352, which comprises a cast-coated paper web and a film formed thereon comprising polyvinyl alcohol having a saponification degree of from 50 to 90 mole % and a crosslinking agent, and a printing sheet for an overhead projector (OHP) as described in Japanese Patent Application Laid-Open No. 60-220750, which comprises a polyester film and a hydrophilic film provided thereon composed of water-soluble polyvinyl alcohol having a saponification degree of from 70 to 90 mole %.
With the improvement in performance of ink-jet printing apparatus, such as speeding up of printing and multi-coloring of images, in recent years, ink-jet printing media have been also required to have higher and wider properties.
More specifically, they are required to simultaneously satisfy, for example, the following properties:
(1) having high ink absorptivity (absorbing capacity being great, and absorbing time being short);
(2) providing dots high in optical density and clear in periphery;
(3) providing dots having a substantially round shape and a smooth periphery;
(4) undergoing scarce changes in the properties even at varied temperatures and humidities and no curling;
(5) undergoing no blocking;
(6) being able to stably store images formed thereon for a long period of time without deterioration (in particular, in a high-temperature and high-humidity environment);
(7) being stable without undergoing deterioration even when stored for a long period of time (in particular, in a high-temperature and high-humidity environment); and
(8) having good feeding property so as to smoothly move when charged into a printer and printed.
More recently, printing media have been strongly requested to have good continuous feeding property in various printers.
Besides, printing sheets for OHP and the like are further required to have excellent transparency in addition to the above requirements.
These properties are often in a relation of trade-off. It has hence been impossible to satisfy them at the same time by the conventionally known techniques. For example, the exemplified recording media of the prior art have comparable performance in dot shape and blocking resistance, but are poor in ink absorptivity. Therefore, they cause image smearing and unevenness of color strength due to ink running at areas high in image density, i.e., areas great in shot-in ink quantity. In addition, they cause color muddiness due to mixing of colors at boundaries between different colors, particularly, in the case of color printing.
Further, it has recently been reported to use inks in which values of physical properties such as surface tension are different between a black ink and color inks to lessen bleeding between the black ink and the color inks. However, there are few examples of a printing material which exhibits good printability to all the inks different in physical property values. Further, any film for OHP satisfying the overall performance taking other properties such as fixing ability into consideration has not been yet obtained.
With the progress of speeding up of recording, increasing of image density and coloring of images, and diversification of inks, as described above, defective ink fixing, deteriorated image quality and lowered shelf stability of the resulting print have become serious problems.
Besides, in these existing constructions, no attention is paid to improvement in feeding property and continuous feeding property in various printers, which is particularly strongly required at present, as to the film for OHP, glossy paper or the like. Therefore, a major problem has been left in this respect. It has been scarcely proposed at present to improve the feeding property and continuous feeding property, and so such a problem must be solved.
Further, as described in, for example, Japanese Patent Application Laid-Open Nos. 59-95188, 57-93193 and 62-170383, it has been reported to use an aqueous resin emulsion as a material of an ink-receiving layer. According to these compositions, an improving effect is recognized to some extent as to blocking. However, no improving effect is recognized as to the problem of the feeding property and continuous feeding property.
In addition, these printing media cause image smearing and unevenness of color strength due to ink running at areas high in image density, i.e., areas great in shot-in ink quantity.
It is thus an object of the present invention to provide a light-transmitting or surface-gloss printing medium which satisfies both of image properties and properties of printing medium itself such as blocking resistance, and feeding property and continuous feeding property in various printers in a well-balanced relation, and an ink-jet printing method using this printing medium, and moreover to provide a light-transmitting or surface-gloss printing medium excellent in fixing ability, stackability after printing and the like, and an ink-jet printing method using this printing medium.
Another object of the present invention is to provide a printing medium which scarcely undergoes deterioration even when the printing medium itself or an image formed thereon is left to stand for a long period of time in a high-temperature and high-humidity environment, and is excellent in fixing ability, stackability after printing and the like, and an ink-jet printing method using this printing medium.
The above objects can be achieved by the present invention described below.
According to the present invention, there is thus provided a printing medium comprising a base material and an ink-receiving layer which comprises inorganic fine particles and a binder and is provided on the base material, wherein the inorganic fine particles are partly projected from a binder layer of the ink-receiving layer and contained in a proportion of 0.05 to 3 parts per 100 parts of the binder in terms of solids.
According to the present invention, there is also provided a printing medium comprising a base material and an ink-receiving layer provided on at least one side of the base material, wherein the ink-receiving layer has a structure that resin particles are held in a continuous film of a water-soluble resin, and inorganic fine particles are partly projected from the surface of the ink-receiving layer.
According to the present invention, there is further provided an ink-jet printing method comprising ejecting an ink on any one of the printing media described above from an orifice of a recording head in accordance with a recording signal, thereby conducting printing.
According to the present invention, there is still further provided a process for producing a printing medium comprising a base material and an ink-receiving layer provided on at least one side of the base material, which comprises applying a coating formulation comprising, as essential components, cationically modified polyvinyl alcohol, an aqueous resin emulsion and inorganic fine particles to the base material to form the ink-receiving layer in such a manner that the resulting ink-receiving layer has a structure that resin particles from the aqueous resin emulsion are held in the ink-receiving layer, and the inorganic fine particles are partly projected from the surface of the ink-receiving layer.
According to the present invention, there is yet still further provided a printing medium comprising a base material and an ink-receiving layer provided on at least one side of the base material, wherein the ink-receiving layer comprises, as essential components, a water-soluble resin, a copolymer of vinylpyrrolidone and a hydrophobic monomer, and inorganic fine particles, and the inorganic fine particles are partly projected from the surface of the ink-receiving layer.
According to the present invention, there is yet still further provided a method of forming images, which comprises forming an image on the printing medium described above by means of an ink-jet system.